Elastomeric compositions are used in a wide variety of applications, including tire components such as treads and sidewalls, hoses, belts, footwear components, and vibration isolation devices. The selection of ingredients for the commercial formulation of an elastomeric composition depends upon the balance of properties desired, the application, and the application's end use. For example, running properties of a tire, in particular of a pneumatic tire, are greatly dependent on the rubber composition of the tread, and particularly stringent requirements are therefore placed upon the composition of the tread mixture. A variety of attempts have therefore been made to improve the properties of the tire by varying the polymer components and the fillers in the tread mixture. A factor that has to be taken into account here is that improving one of the properties of the tire often has the concomitant effect of impairing another property. Among the properties that are correlated, where improvement of one of the properties is usually attended by impairment of at least one other property, are the trio of abrasion, rolling resistance and wet grip.
The use of polybutadiene (BR) in rubber mixtures for tire treads can by way of example improve abrasion performance, but this is achieved by reducing wet grip. Another factor important for tires, however, is gasoline consumption, and the tires should therefore have minimized rolling resistance. Improvements achieved in the field of tires, for example, in terms of abrasion and rolling resistance, should therefore as far as possible be achieved at the same level of wet grip.
Therefore, hydrocarbon resins are used in tire rubbers for enhancement of tire performance characteristics such as traction and wear resistance. Truck, Bus, and Radial (TBR) and winter Powertrack Cityracing (PCR) tire treads and tire sidewall compounds can be made of an immiscible blend of natural rubber (NR) and high-cis polybutadiene rubber (cis-BR). For example, EP Patent No. 1526002A1 discloses, for good ease of production, good durability, and good handling of pneumatic tires, a rubber mixture for the tread base which comprises at least one diene rubber, at least one filler, from 0.5 to 10 phr of at least one aromatic hydrocarbon resin, and from 1.5 to 10 phr of at least one fatty acid and/or metal salt of a fatty acid and/or fatty acid derivative. The examples reveal tread base mixtures with 70 phr of natural rubber, 30 phr of polybutadiene, and 2 phr of an aromatic hydrocarbon resin. However, there is only single hydrocarbon resin used in this example.
Various hydrocarbon resins are available that can be used as additives, such as C5 aliphatic resins, C9 aromatic resins, mixed C5/C9 resins, aromatic pure monomer resins, dicyclopentadiene (DCPD) resins, aromatic modified cycloaliphatic resins, coumarone indene resins, rosin resins, terpene resins, modified terpene resins, terpene phenolic resins, and hydrogenated resins thereof. Different resins may differ in chemical composition, molecular structure and molecular weight distribution, and thus may have different impact on properties of elastomeric compositions.
Therefore, there still is a need to develop an elastomeric composition with balanced and adjustable properties by utilizing a blend of hydrocarbon polymer additives.